1. Field of the Invention
The present invention relates to a machine tool control apparatus for controlling a machine tool; in particular, a machine tool equipped with a numerical controller and a safety device, etc. provided around the machine tool.
2. Description of the Related Art
Conventionally, a machine tool is provided with a numerical controller for controlling operation of the machine tool, and an operation panel including instruction input means and display means. The machine tool is configured to enable input of operation instruction from the operation panel and display of an abnormal condition on the operation panel.
In a conventional machine tool, an abnormal condition is typically displayed in the form of character data (including numerals). For example, when an abnormality occurs in a sensor A, a message “Sensor A is Abnormal” or an error code “123” is displayed. However, in the case where a workpiece is mounted on a jig with a slight positional deviation from the correct position, the machine tool may stop without displaying occurrence of an abnormality (hereinafter, such an abnormality will be referred to as “clam-up stop abnormality”). In such a case, even a skilled operator encounters difficulty in specifying a cause of stoppage of the machine tool.
In view of a foregoing, there has been proposed a facility monitor apparatus which displays on a touch-switch-type display unit a screen as shown in FIG. 5 (a ladder circuit corresponding to a step in which an abnormality has occurred (a circuit diagram showing the operation sequence of the step and the completion condition of the step)) when a machine tool has stopped because of occurrence of an abnormality (including clam-up stop abnormality), to thereby facilitate the operator's work for specifying the cause of the abnormality (see Japanese Patent Application Laid-Open (kokai) No. 2003-122427).
In recent years, an increasing number of companies have started operations in foreign countries where production cost is low so as to manufacture products or parts with high price competitiveness. In such a case, in general, skilled workers cannot be recruited in such foreign countries. Further, even in Japan, the number of skilled workers having mastered high-level techniques has decreased, and an increasing number of unskilled workers such as outsource workers tend to be found in production sites.
Although the conventional machine tool typically reports occurrence of an abnormality by use of “character data, ” this is insufficient for unskilled workers. For example, even when a message “Sensor A is Abnormal” is displayed, an unskilled worker cannot cope with the abnormality, because he or she may not know the location where the sensor A is mounted to the machine tool. Further, even when the mounting position of the sensor A is found, the unskilled worker may not know how to repair or replace the sensor A. Moreover, when a clam-up abnormality has occurred, a very long time may be required to specify the cause of the abnormality, and a very long time may be required to resume the operation.
The conventional technique disclosed in the above-mentioned publication suffers the same problem as the conventional machine tool in that an unskilled worker may be unable to find the mounting location of a part (sensor A in the above-described example), which is the cause of an abnormality, and the unskilled worker may not know the steps of repairing or replacing the part. However, in the case of a clam-up abnormality, the disclosed technique facilitates the work of specifying the cause of an abnormality.
Specifically, in the case of a clam-up abnormality, a ladder circuit corresponding to a step in which the machine tool has stopped is displayed, thereby enabling the unskilled worker to successively investigate or check moving parts each corresponding to a sensor, switch, or the like contained in the ladder circuit. Since the range of investigation is automatically narrowed, the cause of an abnormality can be easily specified.
In the case of a ladder circuit as simple as the example shown in FIG. 5 (having six or so elements), sequentially investigating the displayed elements does not require a considerably long time. However, in the case where a worker or operator does not know the locations of moving parts corresponding to the elements to be investigated and/or the worker or operator does not know the shapes of the moving parts, sequentially investigating the moving parts may take a considerably long time.